Topical analgesic composition



United States Patent 2,975,097 TOPICAL ANALGESIC COMPOSITION John Paul Modderno, Gambrills, Md., assignor to Modern-Lab, Incorporated, Baltimore, Md., a corporation of Maryland No Drawing. Filed Nov. 13, 1957, Ser. No. 696,052 9 Claims. (Cl. 167-52) This invention relates to topical analgesic compositions for rapid relief of muscular aches and pain. More particularly, this invention relates to hydrophilic base compositions for topical application having at least one ethyl aminosalicylate, at least one alkyl ester of amino benzoic acid, and at least one chlorinated phenol as the therapeutically active ingredients to effect rapid penetration by the active ingredients into the skin to provide for quick analgesic relief.

The search for more effective topical analgesic agents than those known at present is a never-ending one. Efforts are constantly being made to find compositions which by topical application will rapidly alleviate pain, such as rheumatic muscular aches and pains. Many analgesic compositions have been formulated for topical application to relieve rheumatic and muscular and surface aches and pains, but these compositions have the disadvantage of requiring intense rubbing or massaging of the material into the skin, which often produces chafing of the skin, in order to effect penetration of the active ingredient. This lack of rapid penetration of the active pain relieving ingredients prolongs discomfort and delays the desired relief. Where penetration of the active ingredients is resisted by the skin, only a minor pain relieving effect results. Such compositions also require the application of large quantities of the material in order to obtain pain relieving results, which of course causes discomfort to the user.

The present invention resides in the discovery of a potentiated topical analgesic composition having rapid tissue penetrating powers to bring about increased effectiveness for the relief of pain. It has been found that the combination of at least one of the mono-, di, and triethylamine salicylates, atleast one alkyl ester of amino benzoic acid, and antibacterial chlorinated phenol provides a potentiated active ingredient which, when incorporated in a hydrophilic base carrier, produces rapid and uniform penetration of the ingredients into the skin and tissue to bring about quick relief from muscular aches and pains of the rheumatic type.

The combination of active ingredients of this invention can be incorporated in any type of hydrophilic base, such as an ointment, a cream, a petrochemical base, a base comprised of polymerized resins capable of emulsification, or an aliphatic base. It will be appreciated that these bases act as the carrier of the active ingredients and present a homogeneous medium with the active ingredients thoroughly dispersed therethrough so that application to the body effects uniform medication to the area treated. To the active ingredients and base making up the compositions of this invention can be added minor amounts of other materials, such as parasepts for preventing fungus growth; coolants such as thymol, camphcr, and the like; perfumes; surfactants, and other body treating and soothing compounds.

It has also been found that the active ingredients of this invention can be applied as a sprayby incorporating them in a sprayable carrier for treatment of the body,

For this type of application, a sprayhuman body from a pressurized dispensing device having the ability to apply the spray in a simple and effective Patented Mar. 14, 1961 manner. In this type of applicator, it is particularly desirable to have a carrier and a dispensing gas which Will produce a non-foaming application of the effective ingredients. A standard pressurized dispensing device may be used to apply the spray to the skin. It has been found that a very effective gas, which minimizes the possibility of foaming, is argon, but it will be appreciated that other types of inert gases may be used. It has been found that argon gas does not form a foamable mixture with the material to be sprayed when it is released from the pressurized container but rather acts like a piston so that the composition is projected for effective application to the skin.

There are instances'in which the combined action of two or more drugs is greater than that which can be anticipated from the sum of their individual actions, commonly referred to as potentiation, as set forth by Louis S. Goodman and Alfred Gilman on page ll'of their book The Pharmacological Basis of Therapeutics, 2nd ed., Macmillan Company, New York, 1956. It is believed that the rapidity of pain relief efiected by the compositions of this invention is the result of potentiation.

The rapid penetration of the amino salicylates is believed to be enhanced by the presence of the chlorinated phenol, which produces a beneficial treatment to the skin and which is an antibacterial compound.

These and other objects and advantages will become apparent from an examination of the following description and appended claims.

The compositions of this invention may be in form of a solution or in a hydrophilic base, such as a polymerized resin, cream, ointment, salve, or the like. The principal active analgesic ingredient in the composition is at least one ethyl type aminosalicylate, the mono-, di, or triethylamine salicylates being preferred. The other active ingredients are the local anesthetic alkyl ester of amino benzoic acid, such as the ethyl-para-aminobenzoate (benzocaine), butyl aminobenzoate, piperocaine hydrochloride, and the like, the ethyl-para-aminobenzoate being preferred; and the local antibacterial chlorinated phenols, such as hexachlorophene, p-chlorophenol, chlorothymol, etc, hexachlorophene being preferred. The combination of these active ingredients provides for rapid absorption of medication into the tissues of the body upon application as well as antiseptic, antibacterial and germicidal action which brings about the quick effective medication of the skin to which the active ingredients have been applied, as well as the thorough and rapid penetration of the tissues for effective relief.

Although the proportions of the active ingredients depend upon the application desired, excellent results are obtained when the amino salicylate is in the range of 5 to 15 parts by weight, the alkyl amino benzoate in the range of 0.5 to 2 parts by weight, and the chlorinated phenol in the range of 0.1 to 0.5 part by weight.

The amino salicylate used in the compositions of this invention can be prepared by the following procedure. Diethylamine salicylate, for example, can be prepared by 'reacting stoichiometric quantities of U.S.P. salicylic acid with the niol weight requirement of diethylamine in sufficient water to make a 50% solution. The solution is held at a temperature of 80 C. for three hours in a glass reactor and agitated to insure completion of the reaction and to drive off any excess free amine. The ethylamine by condensation is added onto the carboxyl group of the salicylic acid forming water and diethylamine salicylate.

The free amine or free salicylic acid is determined by titration and the identity of the compound is verified by infrared examination and a comparison with standard infrared curves. Purity of the diethylamine salicylate is determined by taking its melting point and analyzing for nitrogen, carbon and hydrogen content. In like manner,

the monoethylamine and triethylamine salicylates can be formed by addition of the respective amine to the carboXyl group of salicylic acid under condensation conditions.

The following examples are by way of illustration and are not to be considered in any way a limitation of the scope of the compositions forming a part of the invention:

Example 1 Ten percent by weight of diethylarnine salicylate, 0.5% by weight of monoethylamine salicylate, and 0.5% by weight of triethylamine salicylate together with 1.0% of butyl benzocaine and 0.1% of hexachlorophene to which is added 2.0% of glyceryl stearate, 5.0% of a petroleum base oil, 0.5% of lanolin, 2.0% of Span 40, and 2% of Tween 40 were melted together to form a homogeneous mixture. The batch was mixed until it was paste-like in consistency and then 70.9% by weight of water, 5% by weight of glycerol, 0.5 by weight sodium alginate as a protective colloid, and a modicum of perfume were added. The mixing was continued until a creamlike base was formed having the active ingredients thoroughly dispersed therethrough.

The composition thus prepared, when applied to the skin was found to produce rapid alleviation of rheumatic and arthritic pain.

Example II The formulation as set forth in Example I was prepared except that 69.8% of water was used and 0.1% of a propyl parasept was included in the melt to introduce into the medicated composition fungicidal properties. When the medicated cream was applied to the skin, it was found to rapidly reduce rheumatic aches and pains.

Example III Ten percent by weight of diethylaminc salicylate, 0.5% by weight of monoethylamine salicylate, and 0.5% by weight of triethylamine salicylate together with 1.0% of benzocaine and 2.0% of hexachlorophene to which is added 2.0% of a petroleum base oil, 0.5% lanolin, 2.0% of Span 40, 2.0% of Tween 40, 0.3% of thymol, 0.3% of menthol, and 0.3% of camphor were melted together to form a homogeneous mixture. The batch was mixed until it was pastelike in consistency. To the melt was added 68.5% by weight of an 80% isopropanol, 5.0%

by weight Antara CO-630 emulsifier, 5.0% glycerine,

and 0.1% of a propyl parasept. Stirring of the solution continued until the melt was thoroughly mixed. The analgesic composition was placed in an aerosol container, pressurized, and upon spraying on the feet, was found to produce a rapid alleviation of pain normal to tired feet. The spray was also found to inhibit effectively fungicidal growth occasioned by the disease known as athletes foot.

In order to emulsify the compositions of this invention, Tween 40 and Span 40 were employed. Tween 40 is an emulsifying, wetting, dispersing, and detergent agent produced and sold by Atlas Powder Company and is listed in their trade catalog as a polyoxyalkylene ether of partial palmitic acid ester. Span 40 is also an Atlas Powder Company product sold as an emulsifying agent and is described as sorbitan monopalmitate. other minor ingredients used to formulate the compositions of this invention are well-known and their names have become accepted in the art.

It will be understood that many non-active ingredients other than those illustrated above may be incorporated in the compositions of this invention to produce a variety of effects on the skin of the user or to affect the degree of emulsification, surfactant properties, etc.

It will be appreciated that the percentage of the various amino salicylates may be varied to produce the same or equivalent results, or that one or more of the amino salicylates may be used. For example, it was found that compositions made in accordance with Examples I and III in which the salicylates varied from 5% to 15% pro- All of the duced excellent results in the relief of pain, as heretofore described. The amount of benzocaine or its equivalent, when varied from 0.5 to 2.0% in the compositions of this invention, also provides instant relief of pain. In like manner, the hexachlorophenc, when varied from 0.1% to 0.5% produces the same or equivalent results.

It will be appreciated that the percentages of the various additive ingredients, such as the coolants, surfactants, and fungicides (parasepts), may be varied to produce the desired effects depending upon the degree of surface activity required in the composition. In the case of the use of isopropyl alcohol, used as the major constituent in the therapeutic carrier of the foot analgesic composition, it has been found that other alcohols having like properties may be used to form the base for carrying the medication.

In view of the invention presented herein, it will be appreciated that various modifications to the compositions may be made depending on the individual or particular needs, and it is understood that all compositions having the active ingredients as set forth and contained in the appended claims fall within the spirit and scope of this invention.

What is claimed is:

1. A topical analgesic composition comprising a hydrophilic carrier and a therapeutically active ingredient formed essentially from at least one aminosalicylate selected from the group consisting of monoethylamine salicylate, diethylamine salicylate, and triethylamine salicylate, at least one alkyl ester of amino benzoic acid, and at least one antibacterial chlorinated phenol.

2. The topical analgesic composition as claimed in claim 1 in which the alkyl ester of amino benzoic acid is ethyl-para-aminobenzoate.

3. The topical analgesic composition as claimed in claim 1 in which the antibacterial chlorinated phenol is hexachlorophene.

4. The topical analgesic composition as claimed in claim 1 in which a major portion by weight of said carrier is a hydrophilic alcohol.

5. The topical analgesic composition claim 4 in which the major portion of isopropyl alcohol.

6. The topical analgesic composition as claimed in claim 1 in which said carrier is in an emulsified form.

7. Asprayable topical analgesic composition comprising a liquid hydrophilic carrier having dispersed therethrough at least one aminosalicylate selected from the group consisting of mono-, di-, and triethylaminc salicylates, at least one alkyl ester of amino benzoic acid, at least one antibacterial chlorinated phenol and a propellent gas.

8. The sprayable topical analgesic composition as claimed in claim 7 in which the propellent gas is an inert gas.

9. The sprayable topical analgesic composition as claimed in claim 7 in which the propellent gas is argon.

as claimed in said carrier is References Cited in the file of this patent UNITED STATES PATENTS 1,531,464 Wallis Mar. 31, 1925 2,045,125 Curtis June 23, 1936 2,105,197 McCrea Jan. 11, 1938 2,457,188 Stone Dec. 28, 1948 2,782,975 Bird Feb. 26, 1957 2,801,201 Kipnis July 30, 1957 FOREIGN PATENTS 716,481 Great Britain Oct. 6, 1954 OTHER REFERENCES Ellin et al.: J.A.P.A., Prac. Pharm. Ed., vol. 16, No. 12, December 1955, pp. 747-749.

I.A.M.A., vol. 160, No. 17, April 28, 1956, p. 101.

Dispensatory of U.S., 25th ed. (1955), Lippincott Co., Philadelphia, pp. 640-641. 

1. A TOPICAL ANALGESIC COMPOSITION COMPRISING A HYDROPHILIC CARRIER AND A THERAPEUTICALLY ACTIVE INGREDIENT FORMED ESSENTIALLY FROM AT LEAST ONE AMINOSALICYLATE SELECTED FROM THE GROUP CONSISTING OF MONOETHYLAMINE SALICYLATE, DIETHYLAMINE SALICYLATE, AND TRIETHYLAMINE SALICYLATE, AT LEAST ONE ALKYL ESTER OF AMINO BENZOIC ACID, AND AT LEAST ONE ANTIBACTERIAL CHLORINATED PHENOL. 